Elastically flexible fastener

ABSTRACT

An elastically flexible fastener is provided with separable fastening structure carrying flanges having respective shoulder ribs which normally project to a spacing greater than the spacing between inside surfaces of slider walls and deflectable toward one another to be received between the slider walls and in retaining engagement with slider shoulder structures. Assembly of the slider with the fastener is adapted to be effected by snapping the slider into position by relative transverse assembly movement wherein the slider shoulder structures deflect the fastener shoulder ribs inwardly until the slider shoulder structures have cleared the ribs, whereupon the ribs snap resiliently into engagement with the slider shoulder structures.

United States Patent [191 Laguerre 1 ELASTICALLY FLEXIBLE FASTENER [75]Inventor: Leon Ker Laguerre,

Boulogne-sur-Seine, France [73] Assignee: Minigrip, lnc., Orangeburg,NY.

[22] Filed: June 7, 1971 [21] Appl. No.: 150,329

[30] Foreign Application Priority Data [451 Apr. 30', 1974 3,634,913l/l972 Ausnit 24/201 C FOREIGN PATENTS OR APPLICATIONS 257,510 10/1967Austria 24/201 C Primary Eraminen-Bemtard A. Gelak ABSTRACT Anelastically flexible fastener is provided with separable fasteningstructure carrying flanges having respective shoulder ribs whichnormally project to a spacing greater than the spacing between insidesurfaces of slider walls and deflectable toward one another to bereceived between the slider walls and in retaining engagement withslider shoulder structures. Assembly of the slider with the fastener isadapted to be effected by snapping the slider into position by relativetransverse assembly movement wherein the slider shoulder structuresdeflect the fastener shoulder ribs inwardly until the slider shoulderstructures have cleared the ribs, whereupon the ribs snap resilientlyinto engagement with the slider shoulder structures.

12 Claims, 3 Drawing Figures ELASTICALLY FLEXIBLE FASTENER Thisinvention relates to elastically flexible fasteners and method ofassembling sliders therewith and is more particularly concerned with anarrangement in which the slider is adapted to be assembled with thefastener by a relative transverse maneuver as compared to conventionalendwise assembly.

In my US. Pat. No. 3,426,396, I have disclosed a slider which is adaptedto be assembled with a fastener by relative transverse assemblymaneuver, but wherein the slider has flexible side walls to enableclearance of inwardly projecting shoulders along free edges of theslider walls to clear past the body of the fastener into engagement withgenerally undercut shoulders on the fastener strips and wherein suchshoulders are nroamlly conformed to seat on the shoulder structures ornoses on the slider walls. Such an arrangement is excellent where thefastener strips are of the multi-interlocking rib and groove type inwhich the fastener strips assemble together into a substantially solidmass. In such an arrangement after the slider has been assembled withthe fastener excellent retention of the slider against displacement fromthe fastener by forces acting in a transverse separating direction isattained.

However, there are types of elastically flexible fasteners in whichthere is not the relatively solid body backing, so that after the sliderhas been mounted on the fastener, there may be a tendency for the sliderto separate or come off of the track due to undue flexibility in thearea of the shoulder means on the fastener which thus can yield inwardlyand slip off of the shoulder or nose structure on the slider walls. Itis to the alleviation and solving of this problem that the presentinvention is particularly directed.

An important object of the present invention is to provide a new andimproved elastically flexible fastener expecially equipped for efficientassembly with a slider assembled therewith by a relative transversemaneuver.

Another object of the invention is to provide a separable elasticallyflexible fastener having new and improved means for retainingcooperation with a slider.

A further object of the invention is to provide a new and improvedseparable elastically flexible fastener having novel shoulder meansthereon for secure interengagement with shoulders on a slider.

Still another object of the invention is to provide a new and improvedmethod of assembling a separable elastically flexible fastener and aslider.

Other objects, features and advantages of the invention will be readilyapparent from the following description of a preferred embodimentthereof, taken in conjunction with the accompanying drawing, althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concepts embodied in the disclosure, andin which:

FIG. 1 is a transverse sectional view through a separable elasticallyflexible fastener embodying features of the invention;

FIG. 2 is a similar view of the fastener illustrating the method ofassembling a slider therewith; and

FIG. 3 is a similar sectional view of the fastener showing the sliderfully assembled therewith.

By way of example, a separable elastically flexible fastener of the typegenerally represented by the disclosure in US Pat. No. 3,347,298 hasbeen depicted in the drawing and includes (FIG. 1) a rib element part 5separably receivable in a groove element part 7. These parts areintegrally carried respectively on inner faces of and between alignedlower and upper sections of spaced generally parallel flange portions 8and 9, which are of generally the same thickness. While the flangeportions 8 and 9 may be fastener strips adapted to be secured in asuitable manner to flexible walls of a reclosable container, theseflanges may be the actual integral marginal portions of such walls. Inany event, the separably interlocking complementary profiled fasteningstructure andthe flange portions 8 and are adapted to be integrallyextruded from suitable synthetic plastic material providing anelastically, resiliently flexible construction.

For separable interlocking of the rib element 5 with the groove element7, the rib element is of generally arrow-shape in transverse crosssection including a head 10 comprising interlock shoulder hook portions1 1 and 12 generally convergently related to provide a cam ridge 13generally aligned with a stem flange 14 by which the head is connectedin spaced relation with respect to the supporting flange portion 8. Attheir surfaces nearest the connecting stem flange 14, the shoulderportions 11 and 12 define reentrant angles therewith providing interlockhooks engageable-with interlock hook flanges l5 and 17 respectively ofthe groove element 7. Said hook flanges generally converge toward oneanother and are spread open to receive the head 10 therebetween whensaid head is pressed into said groove-element 7 until the head is fullyreceived in a groove 18 of said groove element 7 generally complementaryto the head and within which the head is interlocked by interengagementof the head shoulder hook portions 1 1 and 12 and the groove hookflanges 15 and 17. Through this arrangement, as indicated, the head andgroove elements 5 and 7 are adapted to be interlockingly engaged bybeing pressed together and to be separated when forcably pulled apart,as by means of a generally U-shaped slider 19 (FIGS. 2 and 3).

By preference, the slider 19 is of the kind described din my US. Pat.No. 3,426,396, including a flat back plate 20 adapted to run along freeedges 21 on the upper ends of the sections of the flange portions 8 and9 as shown in the-drawing. Integrally formed with the back plate 20 andextending in the same direction (downwardly as shown) therefrom arerespective coextensive side walls 22 with an intermediate spreaderfinger 23 extending in the same direction as the side walls at one endof the slider. It will be appreciated, of course, that the side walls 22are in the form of panels which are laterally divergent from a narrowerend of the slider where the flange portions 8 and 9 are in the nearestapproach to one another with the profiled interlocking complementaryfastening structure fully interengaged, to a maximum width at theopposite end of the slider where the separating finger 23 is located,and the fastening structure rib and groove elements separated thereby.Thus, a movement of the slider 19 along the elastically flexiblefastener in one direction causes the fastener to be closed and movementof the slider along the fastener in the opposite direction causes thefastener to be opened.

In order to retain the slider 19 against transverse displacement fromthe fastener, that is, against displacement away from the edges 21, theslider walls 22 are each provided with an inwardly projecting shoudlerstructure 24 flange adapted to engage respective shoulder ribs 25 and 27on respectively outer sides of the lower sections of the flange portions8 and 9. In a desirable arrangement, the shoulder flanges 24 areinwardly projecting nose flange formations on the terminal or free endportions of the side walls 22 having respective substantially flatshoulder surfaces 28 which extend generally perpendicularly inwardlyfrom the inner surfaces of the side walls 22 and face toward and areparallel with the inner surface of the body plate 20 and against whichgenerally complementary confronting shoulder surfaces 29 on the shoulderribs 25 and 27 are engaged in the assembly. Although the shoulderflanges 24 may be provided at either end of the slider 19, a preferredlocation is at the narrow end where maximum assurance againstunintentional pulling of the slider away from the fastener is hadbecause the fastener is fully closed and closely confined by the sliderwalls 22. This is also desirable where the fastener does not haveadditional nose flanges located on the separating finger that engageunder the fastener parts 5 and 7 at the wider end of the slider.

Substantial improvement in retention of the slider 19 on the fastener isattained by having the shoulder ribs 25 and 27 constructed and arrangedto be biased firmly into the reentrant angle defined by the respectiveshoulder surface 28 and the adjacent inner wall surface of the slider.To this end, the ribs 25 and 27, when not in engagement with the slider,normally project to a spacing which is greater than the spacing betweenthe inside surfaces of the slider walls 22 at least adjacent to theshoulder flanges 24. When the slider is transversely moved over thefastener, the ribs are compressively deflected inwardly toward oneanother to be finally received in outwardly thrusting relation betweenthe slider walls and in retaining engagement with the slider shoulderstructures.

The ribs are so designed that their outward thrust, when engaged by theslider walls, is not great enough to impair the movement of the slideralong the fastener. The desirable construction of the shoulder ribs 25and 27, for this purpose, is as shown in FIG. 1, wherein said ribs areprogressively slanted from their fastener strip flange portions to theirrespective shoulder surfaces 29, so that in each instance said surfaceis normally at an angle calculated to engage firmly and uniformly withthe confronting slider shoulder surface 28 when the angle A is flattenedout to become substantially parallel with the engaging surface of theassociated slider side wall 22, as best seen in FIG. 3. Advantageously,the progressive thickening of the ribs 25 and 27 toward the shoulders29, and the consequent progressive resilient stiffening given to theshoulders increases up to the re-. quired limit the outward thrustpressure under compression in the full assembly, as the mass of materialin the shoulders tends to spring back toward normal.

A further advantage of having the shoulder ribs 25 and 27 slanted alongthe angles A, generally away from the edges 21 is that in applying theslider 19 to the fastener by transverse assembly, the shoulder flanges24 can without undue resistance press the ribs 25 and 27 inwardly towardone another, as shown in FIG. 2 until the shoulder surfaces 28 havecleared and receive the rib shoulder surfaces 29. To facilitate thisaction, the surfaces of the shoulder flanges 24 which face in theopposite downward direction relative to the shoulder surfaces 28 aredesirably formed to provide lead-in respective slanting cam surfaces 30which may be rounded as shown. At the ends where the slider side walls22 have their greatest resiliency, passage of the shoulder structures 24past theshoulder ribs 25 and 27 is further eased by expansible yieldingof this part of the slider walls in response to resistance to pressingof the shoulder ribs inwardly beyond the respective normal planes of theinner surfaces of the slider side walls. Additional means to ease theassembly interengagement is afforded by respective relief slots 31extending into the rib shoulders 29 aligned with the normal adjacentsurface of the respective flange portion 8 or 9. These longitudinalslots 31 are also advantageous during the extrusion molding of thestrips to avoid pulling-in deformation of the rib structure due toshrinkage in the setting or curing of the material.

Another feature in avoiding undue resistance to movement of the slider19 into assembly with the fastener, comprises having the shoulder ribstructures 25 and 27 located on the lower sections of the flangeportions 8 and 9 below the complementary profiled fastening structureparts so as to permit relative inward displacement of the lower sectionsof the flange portions 8 and 9 in the rib areas thereof under and towardthe fastening structure parts with some clearance. For example, asindicated in FIG. 1, the clearance afforded for this purpose isrepresented by the angular lines B. In the normal, undefomed conditionof the fastener strip flange portions 8 and 9, the angles which arerepresented by the lines B and extending from the same point on theouter surfaces of the flange portions 8 and 9 as the angles A, aregreater than the angles A, considered with respect to the flange portionouter surfaces, so that as the rib areas of the flange portions aredeflected inwardly toward one another generally about axes at theconvergence of the angles A and B there will be minimum pressure againstthe fastening structure profiles during assembly, and until the shoulderribs have snapped into theirinterlocking relation with the slider on thefastener, the rib areasof the flange portions 8 and 9 while remaininginwardly deflected will remain free from pressing against the adjacentprofiled fastening structure, thus avoiding excess pressure against theslider walls and enabling easy normal functioning of the slider alongthe length of the fastener. This relationship is enhanced by having theshoulder ribs 25 and 27 respectively of less thickness than clearancespacing between the fastening structure 5, 7 and the inner sides ofthose lower sections of the flange portions 8 and 9 carrying theshoulder ribs.

Although the slider 19 may be molded from a semihard plastic, whereinthe side walls 22 are stiffly resiliently flexible at least sufficientto enable spreading apart of the terminal portions of the side wallswhen the shoulder structures 24 are moved transversely in engagementwith the flange portions 8 and 9 past the profiled engaged fasteningstructure and the ribs 25 and 27, it may be desirable to form the slider19 from metal as a die casting or molding, or to mold the same from ahard synthetic plastic material such as one of the thermo-settingmaterials. Where the profiled fastening structure of the fastener is ofthe type particularly selected for illustrative purposes herein, thereis enough yieldability in the connecting web flange l4 and adjacentportions of the fastening structure to enable sufficient elasticdeformation-while moving the slider shoulder flanges 24 past thefastening structure along the flange portions 8 and 9 for transverserelative assembly movement, even though the shoulder flanges 24 do notyield during the assembly action.

After full assembly of the slider 19 with the fastener has beeneffected, not only does the resilience of the mass of the shoulder ribs25 and 27 and the contiguous area of the flange portions 8 and 9function to maintain a firm interlocked relation to the shoulder flanges24 of the slider, but the adjacency of the inner surfaces of the flangeportions 8 and 9 to the adjacent portion of the groove element 7 alsoserves to impede back-off of the shoulder ribs, because to escape theshoulder flanges 24, the deflection of the flange portions 8 and 9 mustbe to the extent of causing compression of the adjacent portion of thehook element 7 as shown in FIG. 2, thus adding the resistance todeformation of that portion of the element 7 to the resistance todeflectional deformation of the flange portions 8 and 9 and the ribs 25and 27. In addition, by reason of the partial separation of the ribs 25and 27 by the slots 31, even though compressively closed in theassembled relationship of the parts, the shoulder ribs can remain intheir interlocking relation to the slider shoulder flanges 24 whilepermitting free deflectional yielding of the flange lower sections'ofthe portions 8 and 9 below the ribs to a substantial extent as indicatedin dash outline, for example, in FIG. 3 without affecting the shoulderribs. Pulling forces on the flange portions 8 and 9 are also moreeffectively resisted because of the separation effected by the slots 31because the shouldering portions of the ribs by compressing against theshoulder flanges 24 develop increasing resistance to release from theshoulder portions as the pulling force increases.

An additional advantage of ribs and 27, is, that if properly designed,when they are in assembled relationship with the slider, they keep thelower part of the flanges 8 and 9 away from slider shoulder structureinner edge tips 32 and 33, which have a tendency to cut the flanges whenmoved back and forth in normal use. This can be accomplished by havingthe ribs thicker than the width of the shoulder structures. As shown,the lower slanting surfaces of the slider flanges 24 extend generallyoutwardly from the respective inner edges 32 and 33.

It will be understood that variations and modifications may be effectedwithout departing from the spirit and scope of the novel concepts ofthis invention.

I claim:

1. A flexible fastener of the kind having separably interlockingcomplementary profiled fastening structure adjacent to free edges offlange portions, and a fastener closing and opening slider of generallyU-shape straddling said free edges and having side walls along saidflange portions each' provided with an inwardly projecting slider flangethe improvement comprising respective shoulder ribs on outer sides ofsaid flange portions spaced from said free edges and engaged by saidslider shoulder flanges;

said ribs normally projecting to a spaced relation which is greater thanthe spacing between inside surfaces of said slider walls adjacent tosaid shoulder flanges and being compressibly resiliently deflectedinwardly toward one another by said walls into conformity with saidspacing;

said ribs being located below said fastening structure and havingrespective outer surface which slant from the associated flange portionouter sides; and

sufficient clearance being provided between the inner sides of saidflange portions in the parts thereof aligned with said shoulder ribs toenable deflection of said parts inwardly to angles greater than theslanting angle of said outer surfaces when the ribs are inwardlydeflected.-

2. A flexible fastener of the kind having separably interlockingcomplementary profiled fastening structure adjacent to free edges offlange portions, and a fastener closing and opening slider of generallyU-shape straddling said free edges and having side walls along saidflange portions each provided with an inwardly projecting slider flange,the improvement comprising respective shoulder ribs on outer sides ofsaid flange portions spaced from said free edges and engaged by saidslider shoulder flanges;

said ribs normally projecting to a spaced relation which is greater thanthe spacing between inside surfaces of said slider walls adjacent tosaid shoulder flanges and being compressibly resiliently deflectedinwardly toward one another by said walls into conformity with saidspacing; and

said ribs slanting generally away from said edges and becomingprogressively thicker, terminating in shoulders which face generallyaway from said edges to engage said flanges.

3. A, fastener according to claim 2, in which said shoulders normallyextend relatively divergently to the associated flange portions and aremoved into alignment with said free flange edges but facing in theopposite direction when in engagement with said shoulder structures.

4. A flexible fastener of the kind having separably interlockingcomplementary profiled fastening structures adjacent to free edges offlange portions from which the fastening structures project toward oneanother, and a slider of generally U-shape assembled with the fastenerand having side walls each provided with an inwardly projecting shoulderflange on the free marginal portion of the side wall, comprising:

respective ribs on outer sides of said flange portions spaced from saidfree edges;

said ribs being compressibly deflected inwardly toward one another froma greater spacing than the spacing between the inside surfaces of saidslider walls;

said ribs received in limited outwardly thrusting relation between andagainst said slider walls and in retaining engagement with said shoulderflanges; said ribs having slider-wall engaging surfaces which in normaluncompressed condition of the ribs slant outwardly and generally awayfrom said free edges whereby to facilitate assembling of the slider ontothe fastener by a relative transverse assembly movement toward saidedges and along said flange portions and with said shoulder flangescamming along said surfaces and thereby compressibly deflecting the ribsinwardly toward one another; and said ribs having shoulders thereonwhich in the full assembly of the slider with the fastener areretainingly engaged with said shoulder flanges; said rib shoulderscomprising surfaces which in the uncompressed condition of the ribsslant outwardly and generally toward said edges at an angle whichenables substantially square face-to-face engagement between said ribshoulders and corresponding shoulder surfaces on said shoulder flangesof the slider. 5. A flexible fastener of the kind having separablyinterlocking complementary profiled faening structure and a fastenerclosing and opening slider of generally U-shape having a back plate and.spaced side walls each provided with a single inwardly projecting sliderflange, and wherein:

said fastener comprises a pair of spaced generally parallel flangeportions each having an inner face and an outer face and each carryingon its inner face a respective part of the fastening structure:

each of said flange portions having an upper section extending upwardlyfrom the associated fastener part to a respective free edge and a lowersection extending downwardly relative to the associated fastener part,and said sections of each flange portion being aligned and of generallythe same thickness;

respective fastener-retaining ribs on the outer faces of said lowerflange sections and said ribs being located below the fasteningstructures;

said ribs having respective surfaces facing generally upwardly;

said slider back plate engaging said free edges and said side wallsengaging the outer facesof said flange sections;

an inwardly projecting flange on each of said slider side walls providedwith a substantially flat shoulder surface extending generallyperpendicularly inwardly from the inner surface of the side wall andterminating at a terminous inner edge which is adjacent to theassociated lower flange section;

each of said slider flanges having a lower surface extending generallyoutwardly from said inner edge;

at least one of said rib surface and said lower slider flange surface ateach side of the fastener and slider providing a slanting cam facetofacilitate slipping of the slider flanges past said ribs duringlateral assembly of the slider over the fastener; and

said lower flange sections with said ribs being swingably deflectableinwardly under and toward the fastener parts and thereby facilitatinginward compressible deflection of the lower flange sections and the ribsfor passage of the slider flanges past the ribs I during said lateralassembly and then spring back to effect biased outward thrust of theribs into retaining engagement with said slider flange shouldersurfaces.

6. A flexible fastener according to claim 5, in which said ribs arethicker than the inwardly extending length of said slider shoulderflanges so that the inner edges of said shoulder flanges will remainspaced from the adjacent outer sides of said lower flange portionsections.

7. A flexible fastener according to claim 5, wherein the inwardlydeflected lower flange sections engage with the fastening structure andthpreby assist in maintaining said ribs in retainingengagement with saidslider flange shoulder surfaces.

8. A flexible fastener according to claim 5, wherein said ribs arepartially separated from said lower flange sections so that said lowerflange sections can be freely flexed away from the ribs at theseparations without tending to displace the ribs from said slider flangeshoulder surfaces.

9. A flexible fastener according to claim 5, wherein said rib surfacesprovide said cam faces.

10. A flexible fastener according to claim 5,'wherein said slider'flange lower surfaces provide said cam faces.

11. A flexible fastener according to claim 5, wherein said cam faces areprovided by both said rib surfaces and said slider flange lowersurfaces.

12. A flexible fastener according to claim 5, wherein said ribs haveshoulder surfaces which are complementary to and in the retainingengagement with said slider flange surfaces engage flat against theslider flange shoulder surfaces.

1. A flexible fastener of the kind having separably interlockingcomplementary profiled fastening structure adjacent to free edges offlange portions, and a fastener closing and opening slider of generallyU-shape straddling said free edges and having side walls along saidflange portions each provided with an inwardly projecting slider flangethe improvement comprising respective shoulder ribs on outer sides ofsaid flange portions spaced from said free edges and engaged by saidslider shoulder flanges; said ribs normally projecting to a spacedrelation which is greater than the spacing between inside surfaces ofsaid slider walls adjacent to said shoulder flanges and beingcompressibly resiliently deflected inwardly toward one another by saidwalls into conformity with said spacing; said ribs being located belowsaid fastening structure and having respective outer surface which slantfrom the associated flange portion outer sides; and sufficient clearancebeing provided between the inner sides of said flange portions in theparts thereof aligned with said shoulder ribs to enable deflection ofsaid parts inwardly to angles greater than the slanting angle of saidouter surfaces when the ribs are inwardly deflected.
 2. A flexiblefastener of the kind having separably interlocking complementaryprofiled fastening structure adjacent to free edges of flange portions,and a fastener closing and opening slider of generally U-shapestraddling said free edges and having side walls along said flangeportions each provided with an inwardly projecting slider flange, theimprovement comprising respective shoulder ribs on outer sides of saidflange portions spaced from said free edges and engaged by said slidershoulder flanges; said ribs normally projecting to a spaced relationwhich is greater than the spacing between inside surfaces of said sliderwalls adjacent to said shoulder flanges and being compressiblyresiliently deflected inwardly toward one another by said walls intoconformity with said spacing; and said ribS slanting generally away fromsaid edges and becoming progressively thicker, terminating in shoulderswhich face generally away from said edges to engage said flanges.
 3. Afastener according to claim 2, in which said shoulders normally extendrelatively divergently to the associated flange portions and are movedinto alignment with said free flange edges but facing in the oppositedirection when in engagement with said shoulder structures.
 4. Aflexible fastener of the kind having separably interlockingcomplementary profiled fastening structures adjacent to free edges offlange portions from which the fastening structures project toward oneanother, and a slider of generally U-shape assembled with the fastenerand having side walls each provided with an inwardly projecting shoulderflange on the free marginal portion of the side wall, comprising:respective ribs on outer sides of said flange portions spaced from saidfree edges; said ribs being compressibly deflected inwardly toward oneanother from a greater spacing than the spacing between the insidesurfaces of said slider walls; said ribs received in limited outwardlythrusting relation between and against said slider walls and inretaining engagement with said shoulder flanges; said ribs havingslider-wall engaging surfaces which in normal uncompressed condition ofthe ribs slant outwardly and generally away from said free edges wherebyto facilitate assembling of the slider onto the fastener by a relativetransverse assembly movement toward said edges and along said flangeportions and with said shoulder flanges camming along said surfaces andthereby compressibly deflecting the ribs inwardly toward one another;and said ribs having shoulders thereon which in the full assembly of theslider with the fastener are retainingly engaged with said shoulderflanges; said rib shoulders comprising surfaces which in theuncompressed condition of the ribs slant outwardly and generally towardsaid edges at an angle which enables substantially square face-to-faceengagement between said rib shoulders and corresponding shouldersurfaces on said shoulder flanges of the slider.
 5. A flexible fastenerof the kind having separably interlocking complementary profiled faeningstructure and a fastener closing and opening slider of generally U-shapehaving a back plate and spaced side walls each provided with a singleinwardly projecting slider flange, and wherein: said fastener comprisesa pair of spaced generally parallel flange portions each having an innerface and an outer face and each carrying on its inner face a respectivepart of the fastening structure: each of said flange portions having anupper section extending upwardly from the associated fastener part to arespective free edge and a lower section extending downwardly relativeto the associated fastener part, and said sections of each flangeportion being aligned and of generally the same thickness; respectivefastener-retaining ribs on the outer faces of said lower flange sectionsand said ribs being located below the fastening structures; said ribshaving respective surfaces facing generally upwardly; said slider backplate engaging said free edges and said side walls engaging the outerfaces of said flange sections; an inwardly projecting flange on each ofsaid slider side walls provided with a substantially flat shouldersurface extending generally perpendicularly inwardly from the innersurface of the side wall and terminating at a terminous inner edge whichis adjacent to the associated lower flange section; each of said sliderflanges having a lower surface extending generally outwardly from saidinner edge; at least one of said rib surface and said lower sliderflange surface at each side of the fastener and slider providing aslanting cam face to facilitate slipping of the slider flanges past saidribs during lateral assembly of the slider over the fastener; and saidlower flanGe sections with said ribs being swingably deflectableinwardly under and toward the fastener parts and thereby facilitatinginward compressible deflection of the lower flange sections and the ribsfor passage of the slider flanges past the ribs during said lateralassembly and then spring back biased outward thrust of the ribs intoretaining engagement with said slider flange shoulder surfaces.
 6. Aflexible fastener according to claim 5, in which said ribs are thickerthan the inwardly extending length of said slider shoulder flanges sothat the inner edges of said shoulder flanges will remain spaced fromthe adjacent outer sides of said lower flange portion sections.
 7. Aflexible fastener according to claim 5, wherein the inwardly deflectedlower flange sections engage with the fastening structure and thprebyassist in maintaining said ribs in retaining engagement with said sliderflange shoulder surfaces.
 8. A flexible fastener according to claim 5,wherein said ribs are partially separated from said lower flangesections so that said lower flange sections can be freely flexed awayfrom the ribs at the separations without tending to displace the ribsfrom said slider flange shoulder surfaces.
 9. A flexible fasteneraccording to claim 5, wherein said rib surfaces provide said cam faces.10. A flexible fastener according to claim 5, wherein said slider flangelower surfaces provide said cam faces.
 11. A flexible fastener accordingto claim 5, wherein said cam faces are provided by both said ribsurfaces and said slider flange lower surfaces.
 12. A flexible fasteneraccording to claim 5, wherein said ribs have shoulder surfaces which arecomplementary to and in the retaining engagement with said slider flangesurfaces engage flat against the slider flange shoulder surfaces.